1. Field of the Invention
The present invention relates to a disk apparatus for recording/reproducing data on/from an optical disk using a light beam. The present invention also relates to a data recording method for recording data on an optical disk using a light beam. Furthermore, the present invention relates to a data reproduction method for reproducing data from an optical disk using a light beam.
2. Description of the Related Art
A high-density optical disk is achieved by an increase in line density and a reduction of the track pitch. Also, an optical system that irradiates a disk with a laser beam is required to achieve a reduced beam spot size as well as a higher density. The beam spot size is proportional to the wavelength of a light source and is inversely proportional to the numerical aperture (NA) of an objective lens. Therefore, the light source must use a shorter wavelength with increasing density.
The influences of disk tilts on recording/reproduction become more serious with increasing density of an optical disk. If a disk suffers any tilts, the signal recording characteristics lower, and crosstalk upon reproduction of a signal increases. In order to solve such problems, an optical disk apparatus which detects and compensates for any disk tilt has been proposed in Jpn. Pat. Appln. KOKAI Publication No. 2000-232677.
Such disk tilt is not uniform over the entire surface of the disk. For example, more serious disk tilt often appears toward the outer periphery of a disk. On the other hand, data recording/reproduction on/from a disk is often executed continuously over a broad range of a disk. Since such continuous recording/reproduction over a broad range of a disk is influenced by various disk tilts, appropriate recording/reproduction is often disturbed. The technique disclosed in the above reference cannot solve this problem.